Heat sink provided with centrifugal fan

ABSTRACT

The present invention is to provide a heat sink withheat pipe, which is limited in height, not so noisy, compact and highly efficient in radiation, and can lower the temperature inside a casing as a whole more effectively even when it is used in an electronic appliance limited in height such as a personal computer, a game machine or the like. 
     A heat sink with centrifugal fan of the present invention, comprising:
         a cover of a given shape, which has an air intake and an air outlet;   a heat receiving block, which is thermally connected to a heat generating body to be cooled;   a heat conductive bottom, which is thermally connected at one surface to the heat receiving block, and is engaged with the cover to form a space;   a radiation fin part, which is thermally connected to the bottom, has a given shape having at least an air inflow portion, and comprises a plurality of fin parts housed in the space;   a centrifugal fan, which has a rotation axis positioned in a neighborhood of the air inflow portion of the radiation fin part, takes in air from the air intake, generates an air flow toward gap portions formed between adjacent fins of the radiation fin part, and generates an air flow along an inner wall of the cover toward the outlet; and   heat transfer members, which are arranged such that resistance of the air flow generated toward a side of the radiation fin part becomes smaller, and are inserted through the plurality of fin parts to transfer heat from the bottom.

TECHNICAL FIELD

The present invention relates to a heat sink with a centrifugal fan provided with a plurality of radiation fins and a centrifugal fan, and particularly to a heat sink with a centrifugal fan that is compact and characterized by an increased amount of ventilation and highly efficient heat radiation.

BACKGROUND ART

A high-performance heat sink having superior heat radiation efficiency is desired as quantity and density of heat generated by a CPU, a device or the like increase. Further, for an electronic appliance such as a personal computer or a game machine, a compact low-noise heat sink having a limited height and highly efficient heat radiation is desired. Conventionally, a low-cost heat sink made of extruded aluminum is used. A heat sink of extruded material can be produced easily since a heat receiving block and radiation fins are formed integrally with each other. However, the pitch of radiation fins is limited by constraint in production. As a result it is difficult to form radiation fins at a fine pitch.

Further, it becomes difficult for only a combination of a heat receiving block and radiation fins to cope with increase of generated heat quantity. Thus, now, a heat sink combined with a heat pipe is used. Among such heat sinks, widely used is a heat sink of the type that many radiation fins of a thin plate shape are inserted through a plurality of perpendicularly-arranged heat pipes attached at each pipe's one end to a heat receiving block. By using heat pipes in this a way of above mentioned, it is possible to increase a radiation area and fin efficiency, and to radiate a large quantity of generated heat.

Inside a heat pipe, there is a space that becomes a flow channel of working fluid. When the working fluid kept in the space moves or changes its phase by evaporation or condensation, heat is transferred. That is to say, the working fluid is evaporated by heat that is released from a part to be cooled which is transferred by heat conduction through the material of the housing constituting the heat pipe on the heat absorbing side of the heat pipe, and the steam moves to the radiating side of the heat pipe. On the radiating side, the steam of the working fluid is cooled and returns to its liquid phase again. The working liquid that has returned to the liquid phase moves (flows back) to the heat absorbing side again. Such phase change and movement of the working fluid causes heat transfer.

Usually, in the case of a forced cooling system using a heat sink of the type that many radiation fins are inserted through a plurality of perpendicularly-arranged heat pipes connected to a heat receiving block, cooling is performed as follows. That is to say, a fan is attached to a side surface of the radiation fins, heat of a part to be cooled is transferred to the radiation fins through the heat pipes, and the cooling fan forcedly cools the radiation fins.

Patent Document 1: Japanese Un-examined Patent Application Laid-Open No. 11-351769

Patent Document 2: Japanese Un-examined Patent Application Laid-Open No. 2001-210767

DISCLOSURE OF THE INVENTION Problem to be Solved By the Invention

However, in the above-described conventional heat sink provided with a cooling fan, the area of the front surface of the fins is as much as the area of the axial flow fan, and thus the height of the fan tends to be higher. When such a heat sink is used in an electronic appliance, whose height is limited, such as a personal computer, a game machine or the like, the heat sink becomes long horizontally since its radiation fins should be short in height. This makes the radiation fins wider. To cool such radiation fins, it is required to arrange many small-diameter fans, and thus the number of fans combined with the radiation fins becomes larger. At the same time, the noise becomes louder. Further, an exhaust opening of the electronic appliance becomes larger. This as well as the need for ensuring a space for placing various terminals makes the casing of the electronic appliance larger.

Further, as the performance of an electronic appliance becomes higher, many heat generating devices are arranged inside the casing, it is necessary to reduce the temperature inside the casing more efficiently.

Further, conventionally, the position of a heat transfer member for fixing a radiation fin part consisting of a plurality of fins of a thin plate shape is determined by focusing only on the function of transferring heat to the radiation fin part. As a result, there is a problem that an air flow coming from a centrifugal fan to the radiation fin part strikes the heat transfer member, making the air flow turbulent and worsening the radiation efficiency.

Thus, an object of the present invention is to provide a heat sink with centrifugal fan, which is limited in height, not so noisy, compact and highly efficient in radiation, and can lower the temperature inside a casing as a whole more effectively even when it is used in an electronic appliance limited in height such as a personal computer, a game machine or the like.

Means to Solve the Problem

The inventor has kept researching, trying to solve the above-described conventional problems. As a result, the inventor has found that the amount of ventilation inside a casing is remarkably increased and the temperature in the casing can be lowered more efficiently by forming radiation fins layered at given intervals to have an approximately semicircular shape corresponding to a centrifugal fan, and by generating an air flow, other than a flow of air moving through the radiation fin, that rapidly flows along the inner wall of a cover toward an outlet, in a space formed by a highly heat conductive bottom that is thermally connected with the cover and the radiation fins.

That is to say, the centrifugal fan is positioned in the space in a state that one side of the centrifugal fan is opposed to the semicircular air inflow portion of the radiation fins layered at the prescribed intervals and the other side of the centrifugal fan is directly opposed to the inner wall of the cover. As a result, on the side opposed directly to the inner wall of the cover, an air flow is generated by the centrifugal fan to follow along the inner wall of the cover and toward the outlet. Further, high heat radiation efficiency can be obtained since heat transfer members are arranged such that an air flow blown from the air inflow portion of the radiation fin part, flowing through the radiation fin part to emerge from a curve portion, does not impede the air flow that flows along the inner wall of the cover toward the air outlet.

The heat sink with centrifugal fan of the present invention has been made based on the above research results.

A first mode of the invention is a heat sink with centrifugal fan, comprising:

a cover of a given shape, which has an air intake and an air outlet;

a heat receiving block, which is thermally connected to a heat generating body to be cooled;

a heat conductive bottom, which is thermally connected at one surface to the heat receiving block, and is engaged with the cover to form a space;

a radiation fin part, which is thermally connected to the bottom, has a given shape having at least an air inflow portion, and comprises a plurality of fin parts housed in the space;

a centrifugal fan, which has a rotation axis positioned in a neighborhood of the air inflow portion of the radiation fin part, takes in air from the air intake, generates an air flow toward gap portions formed between adjacent fins of the radiation fin part, and generates an air flow along an inner wall of the cover toward the outlet; and

heat transfer members, which are arranged such that resistance of the air flow generated toward a side of the radiation fin part becomes smaller, and are inserted through the plurality of fin parts to transfer heat from the bottom.

A second mode of the invention is a heat sink with centrifugal fan, wherein: the radiation fin part has a plurality of fin edge portions formed by a plurality of thin plate fins layered at prescribed intervals; the plurality of fin edge portions has the air inflow portion of a semicircular shape opposed to at least the centrifugal fan, a curve portion connecting to the air inflow portion and extending along the inner wall of the cover, and an outlet portion opposed to the outlet.

A third mode of the invention is a heat sink with centrifugal fan, wherein: a part of an outer peripheral surface of the centrifugal fan is opposed to the air inflow portion of the semicircular shape of the radiation fin part, and a remaining part of the outer peripheral surface is arranged to oppose the inner wall of the cover, so that the air flow along the inner wall of the cover is generated from a prescribed position of the inner wall of the cover as a start point toward the outlet.

A fourth mode of the invention is a heat sink with centrifugal fan, wherein: the cover has an inflection part of a curve surface forming the inner wall of the cover at a position corresponding to a boundary portion between the air inflow portion and the curve portion of the radiation fin part; and the inflection part causes the air flow along the inner wall of the cover.

A fifth mode of the invention is a heat sink with centrifugal fan, wherein: the radiation fin part has another fin edge portion that is in direct contact with the inner wall of the cover; and an end portion of the another fin edge portion forms the start point.

A sixth mode of the invention is a heat sink with centrifugal fan, wherein: the air outlet is in common with an outlet of the air passing through the radiation fin part and an outlet of the air flowing along the inner wall of the cover.

A seventh mode of the invention is a heat sink with centrifugal fan, wherein: the heat transfer members are arranged in a radial pattern starting from the centrifugal fan.

An eighth mode of the invention is a heat sink with centrifugal fan, wherein: the heat transfer members are arranged such that an air flow blown from the air inflow portion of the radiation fin part, flowing through the radiation fin part, to emerge from the curve portion, does not impede the air flowing along the inner wall toward the air outlet.

A ninth mode of the invention is a heat sink with centrifugal fan, wherein: the heat transfer members consist of heat pipes.

A tenth mode of the invention is a heat sink with centrifugal fan, wherein: the air outlet comprises an outlet for the air passing through the radiation fin part and an outlet for the air flowing along the inner wall of the cover, separately.

An eleventh mode of the invention is a heat sink with centrifugal fan, wherein: the heat receiving block is provided with at least one heat pipe.

A twelfth mode of the invention is a heat sink with centrifugal fan, wherein: the air outlet is provided being directed toward an outside of a casing.

Another mode of the invention is a heat sink with centrifugal fan, wherein: the outlet is provided at one place.

Another mode of the invention is a heat sink with centrifugal fan, wherein: the outlet is provided at a plurality of places.

Another mode of the invention is a heat sink with centrifugal fan, wherein:

the heat sink with centrifugal fan comprises:

a centrifugal fan for sending a swirling air flow from a side of the centrifugal fan;

a radiation fin assembly that is positioned on the side of the centrifugal fan and used for cooling by the swirling air flow sent from the centrifugal fan;

a heat receiving block that is fixed to the radiation fin assembly, and transfers heat from a heat generating body to be cooled to the radiation fin assembly; and a case member that supports the centrifugal fan, the radiation fin assembly and the heat receiving block, and forms an air flow space;

the case member comprises:

first and second plate members for forming the air flow space by positioning the radiation fin assembly between the first and second plate members; and

a side member that covers a part of a side of a space between the first and second plate members, and cooperates with the first and second plate member to form the air flow space;

the radiation fin assembly comprises:

a plurality of radiation fins layered at intervals; and

a group of heat transfer members that are inserted through the layered radiation fins and transfers heat to the radiation fins;

the group of heat transfer members includes a plurality of flat heat transfer members each having a cross section of a flat shape, and the plurality of flat heat transfer members are arranged to be distributed to a plurality of places of the radiation fins; and

the flat heat transfer members are distributed such that all or less flat heat transfer members are arranged in such a way that a longitudinal direction of the cross section of the flat shape is inclined with respect to a radius passing the cross section of the flat shape from a center of rotation of the centrifugal fan toward a same rotation direction as a rotation direction of the swirling air flow, to make an acute angle with the radius.

And, another mode of the invention is a radiation fin assembly, which receives, in a side of the assembly, a swirling air flow sent from a centrifugal fan, and performs cooling by the air flow, wherein:

the radiation fin assembly comprises:

a plurality of radiation fins layered at intervals; and

a group of heat transfer members that are inserted through the layered radiation fins and transfers heat to the radiation fins;

the group of the heat transfer members includes a plurality of flat heat transfer members each having a cross section of a flat shape, and the plurality of flat heat transfer members are arranged to be distributed to a plurality of places of the radiation fins; and

the flat heat transfer members are distributed such that a plurality of heat transfer members are arranged in such a way that a longitudinal direction of the cross section of the flat shape is inclined with respect to a radius passing the cross section of the flat shape from a center of rotation of the centrifugal fan toward a same rotation direction as a rotation direction of the swirling air flow, to make an acute angle with the radius.

EFFECT OF INVENTION

According to the heat sink with centrifugal fan, the centrifugal fan is positioned in a space in a state that one side of the centrifugal fan is opposed to the semicircular air inflow portion of a plurality of thin plate fins layered at the prescribed intervals and the other side of the centrifugal fan is directly opposed to the inner wall surface of the cover. As a result, air flows through the layered thin plate fins toward the outlet, while, on the side opposed directly to the inner wall surface of the cover, the centrifugal fan generates an air flow that flows along the inner wall of the cover toward the outlet. When the air flow is an accelerated flow, it is more effective.

Thus, on the one hand, heat transferred from a heat generating device to the heat receiving block is transferred to a plurality of thin plate fins layered at the prescribed intervals. Then, the heat is discharged to the outside of the casing by air that is generated by the centrifugal fan and flows toward the outlet. On the other hand, on the side opposed directly to the inner wall surface of the cover, the centrifugal fan generates an air flow that is accelerated along the inner wall of the cover toward the outlet. As a result, air in the casing is taken in by the centrifugal fan, and then the air flow generated along the inner wall of the cover discharges the taken-in air to the outside of the casing through the outlet. Thus, since air is directly discharged to the outside of the casing, favorably by an accelerated flow, the amount of ventilation is increased, and increase of the temperature of the air inside the casing as a whole owing to heating by a heat generating body can be suppressed.

Further, the radiation efficiency is large, since the heat transfer members are arranged such that the air flow blown from the air inflow portion of the radiation fin part, flowing through the radiation fin part to emerge from the curve portion does not impede the air flow that flows along the inner wall of the cover toward the air outlet.

Further, a group of the heat transfer members, which are inserted through the layered radiation fins and transfers heat to the radiation fins, includes a plurality of heat transfer members each having a cross section of a flat shape, and these heat transfer members having the cross section of the flat shape are arranged to be distributed to a plurality of places of the radiation fins. As a result, heat tends to be uniformly transferred to the radiation fins. Further, the heat transfer members having the flat cross section are distributed such that a plurality of heat transfer members are arranged in such a way that a longitudinal direction of the cross section of the flat shape is inclined with respect to a radius passing the cross section of the flat shape from a center of rotation of the centrifugal fan toward the same rotation direction as a rotation direction of the swirling air flow, to make an acute angle with the radius. As a result, an area of a heat transfer members that the swirling air flow from the centrifugal fan abuts against becomes smaller. Thus, as a whole, the swirling air flow smoothly flows between the radiation fins, and the cooling efficiency can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing one mode of the heat sink with centrifugal fan of the present invention in a state seen from the front side;

FIG. 2 is a perspective view showing the heat sink with centrifugal fan of FIG. 1 in a state seen from the back side;

FIG. 3 is an exploded view explaining the heat sink with centrifugal fan, FIG. 3( a) showing a cover, FIG. 3( b) a highly heat conductive bottom provided with thin plate fins layered at prescribed intervals, and FIG. 3( c) the centrifugal fan;

FIG. 4 is a view explaining an air flow in the heat sink with centrifugal fan according to the present invention;

FIG. 5 is a view explaining an air flow in the heat sink with centrifugal fan according to the present invention;

FIG. 6 is a view explaining an air flow in the heat sink with centrifugal fan according to the present invention;

FIG. 7 is a partially cutaway perspective view showing another mode of the heat sink with centrifugal fan of the present invention;

FIG. 8 is a perspective view showing another mode of the heat sink with centrifugal fan;

FIG. 9 is a cross section of FIG. 8;

FIG. 10 is a sectional view showing schematically a coupling portion between a first plate member and a third plate member;

FIG. 11 is a perspective view showing a state that the first plate member and the third plate member are coupled, each being mounted with a radiation fin assembly;

FIG. 12 is a perspective view showing the first plate member mounted with the radiation fin assembly in a state before the coupling with the third plate member;

FIG. 13 is a perspective view showing the third plate member mounted with the radiation fin assembly in a state before the coupling with the first plate member;

FIG. 14 is a perspective view showing a state that the first plate member and the third plate member are coupled, each being mounted with its radiation fin assembly;

FIG. 15 is a perspective view showing a state that the first plate member and the third plate member, each mounted with its radiation fin assembly, are coupled, and further a second plate member is mounted;

FIG. 16 is a sectional view showing partly a state that flat heat transfer member are inserted through a radiation fin assembly;

FIG. 17 is a perspective view showing a state that the heat sink with centrifugal fan of the second embodiment of the present invention is mounted on a board assembly;

FIG. 18 is a perspective view showing a state before the heat sink with centrifugal fan of the second embodiment is fixed to the board assembly;

FIG. 19 is a schematic sectional view showing structure of pressing an IC chip to be contacted with a heat receiving block;

FIG. 20 is an explanatory view showing distribution of heat transfer members in the heat sink with centrifugal fan of the second embodiment of the present invention; and

FIG. 21 is an explanatory view showing a mechanism for absorbing a difference in height between radiation fin assemblies.

BEST MODE FOR CARRYING OUT THE INVENTION

The heat sink with centrifugal fan of the present invention will be described referring to the drawings. First, referring to FIG. 1 through FIG. 6, a first embodiment will be described. Then, referring to FIG. 7 through FIG. 21, a second embodiment will be described.

One mode of the present invention is a heat sink with centrifugal fan, comprising:

a cover of a given shape, which has an air intake and an air outlet;

a heat receiving block, which is thermally connected to a heat generating body to be cooled;

a heat conductive bottom, which is thermally connected at one surface to the heat receiving block, and is engaged with the cover to form a space;

a radiation fin part, which is thermally connected to the bottom, has a given shape having at least a circumferential air inflow portion, and comprises a plurality of thin plate fins layered at prescribed intervals and housed in the space;

a centrifugal fan, which is positioned in the space such that the centrifugal fan is opposed to the air inflow portion of the radiation fin part and a rotation axis of the centrifugal fan becomes approximately perpendicular to the thin plate fins, takes in air from the downward and/or upward direction with respect to the radiation fin part, discharges a part of the air toward the side of the radiation fin part, and generates an air flow along an inner wall of the cover toward the air outlet; and

heat transfer members, which are arranged such that resistance of the air flow generated toward a side of the radiation fin part becomes smaller, and are inserted through the plurality of fin parts to transfer heat from the bottom.

FIG. 1 is a perspective view showing one mode of the heat sink with centrifugal fan of the present invention in a state seen from the front side. And, FIG. 2 is a perspective view showing the heat sink with centrifugal fan of FIG. 1 in a state seen from the back side.

As shown in FIG. 1, the heat sink with centrifugal fan 1 comprises: a cover 2 of a given shape having an air intake to a centrifugal fan and an outlet for air passing the inside of the heat sink; and a heat conductive bottom 3 that is engaged with the cover 2 to form a space, one surface of the bottom 3 being thermally connected with a heat receiving block. A centrifugal fan 4 is fitted in the air intake. Thin plate fins 5 that are placed in the space and layered at prescribed intervals can be seen in a part of the air outlet. Further, heat transfer members 23, which are inserted through the plurality of thin plate fins for transferring heat of a heat generating body from the bottom to the plurality of thin plate fins, are partly exposed in the surface of the cover 2.

As shown in FIG. 2, the back side of the heat conductive bottom 3 is thermally connected with the heat receiving block 6, which in turn thermally connected with the heat generating body that requires cooling. In the case where the heat generating body is placed apart from the heat sink, heat of the heat generating body is transferred to the heat receiving block 6 through heat pipes 7, for example. As shown in FIG. 2, another air intake to the centrifugal fan may be provided so that air is taken in from the back of the heat sink. Although the heat pipes shown are round heat pipes, plate-shaped heat pipes may be used. The number of heat pipes is not limited to two.

As shown in FIGS. 1 and 2, the air outlet for air passing the inside of the heat sink has a space in which the plurality of thin plate fins layered at the prescribed intervals are not positioned. As described in detail later, an air flow, which is accelerated by the centrifugal fan along an inner wall of the cover of the given shape toward the outlet, passes through this space and is exhausted directly to the outside of the casing.

FIG. 3 is an exploded view for explaining the heat sink with centrifugal fan according to the present invention in an disassembled state. FIG. 3( a) shows the cover. FIG. 3( b) shows the heat conductive bottom provided with the thin plate fins layered at the prescribed intervals. And, FIG. 3( c) shows the centrifugal fan.

As shown in FIG. 3( a), the cover 2 is made of, for example, resin or the like, and enclosed by a wall except for the air outlet 11. Above the air intake 10, the cover has an inflection part 16 at which the curved surface forming the wall of the cover 2 is turned. In the surface of the cover 2, holes are formed for receiving heads of the heat transfer members 23. The heat transfer members 23 are arranged so as to reduce resistance to the air flow generated by the centrifugal fan toward the side of a radiation fin part.

As shown in FIG. 3( b), the heat conductive bottom 3 has a shape that generally corresponds to the cover. That is to say, the bottom 3 has: a doughnut-shaped portion 3-1 for receiving the centrifugal fan placed to be opposed to a semicircular air inflow portion of the plurality of thin plate fins layered at the prescribed intervals; and a portion 3-2 on which the thin plate fins layered at the prescribed intervals are placed to be thermally connected with that portion 3-2. The heat conductive bottom 3 has an inflection part 17 corresponding to the inflection part 16 at which the curved surface forming the wall of the cover 2 is turned. The heat transfer members 23, which are inserted through the thin plate fins layered at the prescribed intervals and transfer heat from the bottom to the thin plate fins, are arranged in a radial pattern centering around the centrifugal fan. Further, favorably the heat transfer members 23 are arranged such that a flow of air that is blown from the air inflow portion of the radiation fin part, flows inside the radiation fin part to emerge from a curve portion 13, does not impede the air flow that flows along the inner wall of the cover toward the air outlet. Further, the heat transfer members may consist of heat pipes. In that case also, the heat transfer members are arranged not to impede the above-described air flow.

As shown in FIG. 3( c), the centrifugal fan comprises a plurality of fans (impellers) 4-1 and a peripheral portion 4-2 that is attached to the air intake of the cover. For example, the fans 4-1 are inserted into the space from the outside of the cover and placed at the above-mentioned doughnut-shaped portion. Then, protrusions provided in the peripheral portion 4-2 are fixed to the periphery of the air intake of the cover.

Further, as shown in FIG. 3( b), the radiation fin part 5 has a plurality of fin edge portions formed by the plurality of thin plate fins layered at the prescribed intervals. That is to say, the plurality of fin edge portions comprises: the circumferential (for example, semicircular) air inflow portion 12 opposed at least to the centrifugal fan; the curve portion 13 that connects with the air inflow portion and extends along the inner wall of the cover; and an outlet portion 14 opposed to the outlet. Further, the plurality of thin plate fins layered at the prescribed intervals have the other fin edge portion 15 that contacts with the inner wall surface of the cover.

In addition to the plurality of thin plate fins layered at the prescribed intervals, the radiation fin part may comprises, for example, a plurality of pin fins arranged in parallel with the axial direction of the centrifugal fan so that the plurality of pin fins form the above-described plurality of fin edge portions. Further, curved plate fins may be arranged in a comb teeth shape such that air flows from the air inflow portion toward the outlet portion. In any case, it is sufficient that the radiation fin part has a shape allowing air to flow from the air inflow portion toward the air outlet portion owing to the centrifugal fan.

Assembling the cover, the bottom and the centrifugal fan described above and shown in the FIGS. 3( a), 3(b) and 3(c), the heat sink with centrifugal fan of this invention is formed as shown in FIGS. 1 and 2.

FIGS. 4-6 explain an air flow in the heat sink with centrifugal fan of this invention.

As shown in FIG. 4, in the heat sink with centrifugal fan of this invention, the radiation fin part is placed on only one side of the centrifugal fan. This solves the following problems. That is to say, if the radiation fin part is placed to surround the centrifugal fan, air flow resistance becomes larger and air capacity is reduced. As a result, the amount of ventilation inside the casing is reduced, and the ambient temperature inside the casing rises and temperatures of all the devices rise.

Thus, in the heat sink with centrifugal fan of this invention, ventilation is improved by using: an air flow that passes through the inside of the radiation fins to exchange heat with the radiation fins for cooling; and an accelerated air flow that is generated along the inner wall surface of the cover by utilizing the part where the radiation fins do not exist within the space. In other words, the heat sink with centrifugal fan of this invention includes an idea that a part of air taken in from the air intake of the cover by the centrifugal fan is converted to a rapid flow along the inner wall surface of the cover and exhausted directly through the air outlet to the outside of the casing.

Thus, by converting a part of air taken in from the air intake of the cover by the centrifugal fan to a rapid flow along the inner wall surface of the cover and by exhausting that part of air directly through the air outlet to the outside of the casing, it is possible to cool a heat generating body positioned in the peripheral portion in the casing.

FIG. 4 is a view explaining a direct discharge route, i.e. an air flow generated when a part of air taken in from the air intake of the cover by the centrifugal fan is converted to a rapid flow along the inside wall surface of the cover, to be exhausted directly through the air outlet to the outside of the casing.

As shown in FIG. 4, on the side that is not opposed to the radiation fin part, the centrifugal fan is opposed to the inner wall surface of the cover, as described above. The other fin edge portion 15 of the radiation fin part is in direct contact with the inner wall surface of the cover. Thus, a part of air flow generated by the centrifugal fan flows along the cover's inner wall surface of the semicircular shape, as shown by the arrow 18. Then, at the inflection part 16 where the curved surface forming the cover's wall turns, the air flow is further accelerated as shown by the arrow 19, to become a large flow along the cover's inner wall surface, and goes toward the air outlet. The thus-accelerated large air flow is directly exhausted to the outside of the casing.

It is favorable to design hydrodynamically the shape of the inflection part 16 where the curved surface forming the cover's wall turns (as shown in FIG. 4), as well as the shape of a boundary portion 21 of the curve portion connecting to the semicircular air inflow portion of the radiation fin part and extending along the inner wall of the cover, such that the air flow generated by the centrifugal fan is accelerated along the inner wall of the cover to become a large flow.

FIG. 5 is a view explaining an air flow that passes the inside of the radiation fin part opposed to the centrifugal fan. A flow of air, which is taken in from the air intake and directed by the centrifugal fan toward the opposed semicircular air inflow portion of the radiation fin part, passes radially between the radiation fins as shown by the arrow 22 and flows moderately toward the air outlet, while changing its direction. This flow transfers heat which is generated, for example, by a heat generating body and transferred to the heat receiving block 6 by the heat pipes 7 and then to the radiation fin part, toward the air outlet by the air flow passing through the radiation fin part, so as to discharge the heat to the outside of the casing. The heat transfer members 23 are arranged not to impede the above-mentioned air flow passing through the radiation fin part, and thus a part of the air flow moves toward the curve portion and the other part directly toward the air outlet.

FIG. 6 is a view explaining an air flow in the heat sink with centrifugal fan of this invention. As shown in FIG. 6, there are two type of air flow generated. That is to say, one type of air flow is the flow explained referring to FIG. 4, which is accelerated along the inner wall of the cover to become a large flow to be directly exhausted through the air outlet to the outside of the casing. And, the other type is the flow explained referring to FIG. 5, which transfers heat (i.e. heat of the heat generating body, transferred to the heat receiving block 6 and then to the radiation fin part) toward the air outlet while the flow is passing through the radiation fin part, so as to discharge the heat to the outside of the casing. As a result, it is possible to discharge effectively the heat of the heat generating body thermally connected to the heat receiving block and heat of heat generating bodies positioned in the neighborhood to the outside of the casing. The heat transfer members are arranged such that a turbulent flow does not occur between the two types of air flow described above, i.e. the air flow that is accelerated along the inner wall of the cover to become a large flow and directly exhausted through the air outlet to the outside of the casing and the air flow that passes through the radiation fin part to discharge the heat transferred to the heat receiving block 6 and then to the radiation fin part through the heat transfer members.

The heat receiving block 2 is made of metal material having superior heat conductivity, such as aluminum, copper, or the like. The shape of the heat receiving block may be a circular column, a quadratic prism, a multangular prism or the like, and can be selected suitably according to the shape of a heat generating body. In the case of connecting the heat receiving block 6 to a plurality of heat generating bodies of different heights, a heat receiving surface may be formed to be uneven according to the heat generating bodies.

As described above, to facilitate coupling between the heat receiving block and the heat pipes, it is possible to provide groove portions corresponding to the heat pipes so that the contact area with the heat pipes is broadened and heat conductivity is increased. As the heat pipes, it is favorable to use round heat pipes, although it is not restrictive. It is favorable that each of the heat transfer members is divergent in cross section from the centrifugal fan toward the curve portion 13 and the air outlet portion 14, and further the heat transfer members as a whole are divergent.

Next, another embodiment of the present invention will be described referring to FIGS. 7-21. This embodiment is an example of a heat sink with centrifugal fan that uses heat receiving blocks 400 and 500 (See FIG. 7) and respective radiation fin assemblies 200 and 300 (See FIGS. 12 and 13) for cooling an IC block on which a plurality of (here, two) IC chips are mounted, while these components are cooled by one centrifugal fan 100.

In the present embodiment, as shown in FIGS. 18 and 19, the heat sink with centrifugal fan 1 is fixed to a board assembly 700, and the board assembly 700 comprises: a main frame 710 constructed from a metal plate of, for example, aluminum; a sub-frame 750 constructed similarly; and a substrate 730 that is mounted between the main frame 710 and the sub-frame 750 and mounts IC chips 720 and electronic devices and the like as well as wiring (not shown). The heat sink with centrifugal fan 1 is fixed by inserting fixing bolts 771 and 772 into through-holes 761 and 762 provided in a leaf spring 760, and then through an opening 751 of the sub-frame 750 and through-holes 731, 732 and 711, 712 of the substrate 730 and the main frame 710, to be screwed into respective screw holes 411 and 412 in the heat receiving block 400 (the same goes for the heat receiving block 500). As a result, an IC chip 720 is pressed against and contacted with the heat receiving block 400 through an opening 713 provided in the main frame 710.

Further, the heat receiving block 400 comes to be fixed to the board assembly 700. Under the leaf spring 760, a member 740 for dispersing force is placed. A function of the force dispersing member 740 is to receive the pressure of the leaf spring and disperse the force in all directions of the board so that the force is uniformly applied to the IC chip. By this arrangement, it becomes possible to improve the degree of cohesion between the IC chip and the heat receiving block. Here, FIG. 18 shows a disaggregate state before the fixing. On the other hand, FIG. 17 shows a state that the heat sink with centrifugal fan 1 is fixed to the board assembly. The board assembly is mounted with not only the IC chips but also, for example, a hard disk drive 900 and/or the like as shown in FIG. 17. Thus, accommodation to cooling of such components is also taken into consideration. An air flow sent from the heat sink with centrifugal fan 1 is exhausted from openings 631, 632 and 641. For example, as shown in FIG. 18, an air flow from the radiation fin assembly 300 (whose side is partly shown) is exhausted from the opening 641.

The heat sink with centrifugal fan 1 comprises: the centrifugal fan 100 for sending a swirling air flow from the side of the fan; the radiation fin assemblies 200 and 300 that are placed on the side of the centrifugal fan 100 and serves for cooling by the swirling air flow from the centrifugal fan 100; the heat receiving block 400 that is fixed to the radiation fin assembly 200 and transfers heat from a heat generating body having a need for cooling to the radiation fin assembly 200; a heat receiving block 500 that is fixed to the radiation fin assembly 300 and transfers heat from a heat generating body having a need for cooling to the radiation fin assembly 300; and a case member 600 (See FIG. 7) that support these components and form an air flow space.

The centrifugal fan 100 absorbs air in the axial direction, and sends the air as a swirling air flow from the side of the centrifugal fan 100. In detail, the centrifugal fan 100 comprises: a core 110 (See FIGS. 7, 8, 9 and 17) having a rotary drive part; a plurality of vanes 120; a ring 130 for fixing the vanes 120; an attachment member 140 for attaching the core 110 to a support member 620; attachment lugs 145; and core support pieces 150. The centrifugal fan 100 is fitted in a through-hole 611 provided in the support member 620, and fixed by the attachment member 140 and attachment lugs 145. At the attachment lugs 145, the centrifugal fan 100 is fixed by using fan fixing screw holes 621 shown in FIG. 15 and bolts (not shown), for example.

The case member 600 comprises a plurality of members that are assembled to function as a case having a space inside. The plurality of members include: a first plate member 610 and a third plate member 660 having the opening 611 for making air flow in;; and a second plate member 620 having an opening 622 for making air flow in. Further, the case member 600 include a side member 650 that covers a part of the side of the space formed between the first plate member 610, the third plate member 660 and the second plate member 620. Together with the first plate member 610, the third plate member 660 and the second plate member 620, the side member 650 forms the air flow space when they are assembled. The first plate member 610, the third plate member 660 and the second plate member 620 are made of metal plates, for example. Metal is used because of its large heat conductivity and large mechanical strength.

In the heat sink of the present embodiment, one side of the case member 600 is covered by the first plate member 610 and the third plate member 660, and the other side by the second plate member 620. The second plate member 620 is mounted with the centrifugal fan 100. As shown in FIGS. 8, 12 and 14, the first plate member 610 is extended to have a boundary side 619 of an outward convex arc shape, which is positioned outside of the turning radius of the rotary vanes 120 of the centrifugal fan 100. On the other hand, the third plate member 660 is formed to have a shape coincident with the planar shape of the boundary side 619 so that the third plate member 660 is in contact with the side of the first plate member 610 at the boundary side 619. In other words, the first plate member 610 and the third plate member 660 have such shapes that these members 610 and 660 become just like one plate when they are abutted against each other.

Further, as shown in FIG. 14, it can be said that a space 601 enclosed by the radiation fin assembly 200 and the radiation fin assembly 300 on the first plate member 610 is an area where a swirling air flow is generated by the centrifugal fan.

The first plate member 610 and the third plate member 660 are coupled by coupling mechanisms 690 as shown in FIGS. 7, 8, 10 and 12, for example. That is to say, the first plate member 610 and the third plate member 660 are coupled such that these plate members can be displaced in the thickness direction of these plate members. In the present embodiment, each coupling mechanism 690 comprises: a pawl 691 provided integratedly with the first plate member 610; a portion of the third plate member 660, in which a through-hole 696 to be engaged with the pawl 691 is provided; and a portion of the radiation fin 310, in which a through hole 311 is provided. The pawl 691 comprises an arm 693 and an engage piece 692 extending from the end of the arm 693 in the direction of the rotation axis of the centrifugal fan 100. The length of the engage piece 692 and the height of the arm 693 are determined as magnitudes required for absorbing displacement occurring between the first plate member 610 and the third plate ember 660.

Here, as shown in FIGS. 8 and 12, through-hole 696 is formed in the neighborhood of an edge portion where the third plate member 660 is abutted against the boundary edge 619 of the first plate member 610. The length and width of the through-hole 696 are determined according to an allowable shift of the third plate member into a plane perpendicular to the rotation axis of the centrifugal fan.

A coupling mechanism 690 can be displaced in the direction of the rotation axis. On the other hand, the coupling mechanism 690 restricts the first plate member 610 and the third plate member 660 such that the first plate member 610 and the third plate member 660 do not come to be apart from each other in a plane perpendicular to the rotation axis, and, at the same time, the third plate member 330 does not ride on the first plate member 310.

In the present embodiment, as shown in FIG. 8 for example, the coupling mechanisms 690 are arranged at two places in an inclined manner. In detail, each coupling mechanism 690 is arranged in a direction of the radius from the rotation center 0 of the centrifugal fan. As a result, relative displacement of the third plate member 660 with respect to the first plate member 610 in the same plane is suppressed to be small.

The radiation fin assembly 200 and the heat receiving block 400 are fixed to the first plate member 610. Further, the side member 650 is coupled to the first plate member 610. Further, the first plate member 610 is integratedly provided with a side portion 615 that forms a side surface. For example, the side portion 615 is opposed to one side 212 of the radiation fin assembly 200, to form a bypass 602 between them. Since the radiation fin assembly 200 does not exist in this bypass 602, resistance becomes smaller, and an air flow can flow at high speed. On the inlet side of the bypass 602, a guide portion 603 for guiding the swirling air flow in the tangent direction of swirling is provided. The guide portion 603 is covered on its outer side by the side member 650, there is no opening. Thus, the swirling air flow moves along the inner wall of the side member 650 and flows into the bypass 602.

In the present embodiment, the side member 650 comprises a plurality of members. For example, a side member 651 for covering one side and side members 652 and 653 for covering the corner are used. Each side member 651-653 not only covers the side but also has a function of restricting displacement of the first plate member 610 and the third plate member 660 in the direction of the rotation axis of the centrifugal fan. That is to say, the side members 651-653 have respective pawls 656, 658 that contact with the first plate member 610 and the second plate member 620, to fix the side members to these plate members. In the present embodiment, the side member 650 is formed by plastic molding, because plastic molding can easily form a complex shape.

The case member 600 has a restriction mechanism for restricting a displacement stroke in the thickness direction of the third plate member 660. In detail, as shown in FIGS. 11 and 12, the side member 651 is provided with rotation-axis-direction restricting pieces 659 for restricting displacement in the direction of the rotation axis of the centrifugal fan. The rotation-axis-direction restricting pieces 659 are formed by a pair of restricting pieces 659 a and 659 b that are lined in the direction of the rotation axis and opposed to each other. The restricting piece 695 b is formed to have a groove shape. The second plate member is inserted into and fixed to this groove. Between these restricting pieces 659 a and 659 b, the third plate member 660 and the radiation fin assembly 300 are positioned. As shown by arrow in FIG. 21, these components 660 and 300 can be displaced in the direction of the rotation axis (in the direction of thickness of the plate). However, between the restricting pieces 659 a and 659 b, the displacement is restricted within a range of a given stroke. This displacement stroke is determined by assuming a deviation to a reference position in the height direction when after-mentioned IC chips are actually mounted. In the present embodiment, the displacement stroke is determined within a range that is shorter than the thickness of the third plate member, for example.

As shown in FIG. 13, locking parts 669 are provided at the ends of the third plate member 660. Between the locking parts 669, a locking part 669 in contact with the side member 651 locks the restricting piece 659 a within the limit of the range of the displacement stroke. Further, the other locking part 669 locks a restricting piece (not shown) that corresponds to the restricting piece 659 a and is provided in another side member 653 within the limit of the range of the displacement stroke. As a result, the restriction mechanism restricts displacement of the third plate member 660 (to which the radiation fin assembly 300 is fixed) in the direction of the rotation axis within the limit of the range of the given stroke. However, the restriction (or allowance) by the restriction pieces 659 is, when the heat receiving blocks 400 and 500 in close contact with the respective two IC chips deviate from the respective reference positions in the IC chip surfaces, provided for the purpose of displacing the heat receiving block 500 relatively so as to absorb the deviation and maintain a suitable pressure contact state.

Owing to the above-described coupling mechanism 690, the first plate member 610 and the third plate member 660 can be coupled while having allowance in the direction of the height of the IC chips or the direction of the rotation axis of the centrifugal fan. As a result, workability of operation such as fixing to the substrate is improved. Further, by such arrangement, it becomes possible to cool a plurality of IC chips by the heat sink provided with one centrifugal fan.

The radiation fin assembly 200 comprises: a plurality of radiation fins 211 layered at intervals; and a group of heat transfer members 220 that are inserted into the layered radiation fins 211 and transfer heat to the radiation fins 211. The group of heat transfer members 220 comprise a plurality of flat heat transfer members each having a flat shape in its cross section. These flat heat transfer members 220 are arranged, being dispersed to a plurality of places of the radiation fins 211. The present embodiment uses the radiation fin assembly 300 also. In the following, the flat heat transfer members 220 will be described, though the configuration of the flat heat transfer members 220 is common to flat heat transfer members 320, and thus the description is not repeated.

The flat heat transfer members 220 are made of metal such as aluminum. Each member is formed to have a flat shape in its cross section. The flat cross section has a side of a longitudinal direction, which is longer than the side of the other direction. The flat shape is employed since air resistance can be reduced by arranging the longitudinal direction of the flat shape to be positioned along the air flow. The flat shape may be an ellipse, an oval, or a rectangle, for example.

An important point here is that the longitudinal direction of the flat shape is made to be positioned along the air flow. As the angle of intersection with the air flow becomes larger, the resistance increases. Thus, it is a problem how the heat transfer members should be arranged. As already shown in FIG. 1 and 3, one answer is to arrange the heat transfer members in a radial pattern. By this arrangement, it is possible to expect that the air flow resistance would be reduced to some extent.

In the second embodiment, the above point is further pursued, and the heat transfer members are arranged as follows. That is to say, the flat heat transfer members 220 are distributed such that all of or less heat transfer members 220 are arranged in such a way that the longitudinal direction of the flat cross section shape is inclined with respect to the radius passing that flat cross section shape from the center of rotation of the centrifugal fan toward the same rotation direction as that of the swirling of the air flow, to make an acute angle with that radius.

FIG. 20 shows schematically an example of distribution of the heat transfer members used in the present embodiment. Assuming that the center of the swirling air flow generated by the centrifugal fan is positioned at the center O of rotation of the centrifugal fan, a line segment r, passing through the center of any flat heat transfer member, is drawn from the center of rotation. Further, a line segment k is drawn in the longitudinal direction of the flat heat transfer member in question. By examining an angle θ formed at the segment r in the longitudinal direction and the intersection of the segment k in the radial direction, it is found that all such angles are acute angles in the direction (shown by arrows in FIG. 20) same as the rotation direction of the swirling air flow.

In the present embodiment, all the heat transfer members in the radiation fin assemblies 200 and 300 satisfy the above-described relation. Of course, the effect of the invention can be realized even if not all the heat transfer members satisfy the relation. Thus, even if a small number of heat transfer members do not satisfy the relation because of design requirement, it can be neglected.

As shown in FIG. 16, in the present embodiment, the flat heat transfer members 220 are successively pressed into the through-holes 610 a provided in the first plate member 610 and the through-holes 211 a provided in the radiation fins 211, so that a plurality of radiation fins 211 are layered at intervals. By pressing into a through-hole, an inner peripheral portion of each through-hole 610 a is drawn in to form a ring-shaped band. As a result, each flat heat transfer member 220 is firmly fixed to the radiation fins 211. Further, the contact area between the radiation fins 211 and the flat heat transfer members 220 increases, and there is a merit that the heat transfer efficiency increases.

In addition to the flat heat transfer members, the present embodiment uses pins 250 for positioning and the like are used. It is expected that these pins also have heat transfer effect, and thus these pins function as heat transfer members. Thus, in effect, heat transfer members having a circular cross section exist alongside the above-described heat transfer members in the present embodiment.

As shown in FIG. 7, the heat receiving block 400 comprises: a heat receiving portion 410; and a heat transfer portion 450 for transferring heat received by the heat receiving portion to the radiation fins. The heat receiving portion 410 is made of metal having superior heat conductivity such as copper, for example. The shape of the heat receiving portion 410 can be suitably selected according to the shape of a heat generating device, and may be a circular column, a quadratic prism, a multangular prism, or the like, for example. Further, as the heat transfer portion 450, heat pipes may be used. Of course, this is not restrictive. In the case of the heat receiving block 400, the heat receiving portion 410 is fixed to the first plate member 610. Further, the heat pipes of the heat transfer portion 450 are arranged such that the base end portion of each flat heat transfer member 220 contacts with a heat pipe. By this arrangement, heat can be effectively transferred to the radiation fins.

The heat receiving block 500 comprises a heat receiving portion 510 and a heat transfer portion 550. The heat receiving block 500 is arranged to be suspended such that the heat receiving portion 510 and the heat transfer portion 550 do not contact with the first plate member 610. The heat transfer member 550 is fixed to the third plate member 660. Thus, the heat receiving block 500 can be displaced in conformity with displacement of the third plate member. The heat transfer portion 550 is arranged such that the base end of each flat heat transfer member 320 contacts with the heat transfer portion 550. By this arrangement, the heat transfer performance can be improved.

As described above, according to the second embodiment of the invention, one heat sink with centrifugal fan can cool two chips. Thus, a bulky cooling part can be easily downsized.

The second embodiment has the two radiation fin assemblies. Of course, it is possible to arrange the embodiment to use one radiation fin assembly. It is possible to accommodate the embodiment to that case by making the side member cover the place on which the third plate member 660 is positioned. Of course, it is also possible to enlarge the area of the first plate member and the radiation fin assembly 200, to position them on that part.

Further, since the present embodiment has the bypass, it is possible to send an air flow at high speed under the smaller resistance. Thus, the efficiency of the centrifugal fan can be improved. As a result, this contributes to cooling of devices existing in another area. For example, it is possible to increase the quantity of air for to the hard disk drive shown in FIG. 17.

INDUSTRIAL APPLICABILITY

The present invention provides a cooling device that can be used for cooling an object to be cooled, starting with IC chips mounted on an electronic appliance such as a computer, a control unit, a game machine, or the like. The present invention can be applied to cooling of an object that can be cooled by using radiation fins and a centrifugal fan. 

1. A heat sink with centrifugal fan, comprising: a cover of a given shape, which has an air intake and an air outlet; a heat receiving block, which is thermally connected to a heat generating body to be cooled; a heat conductive bottom, which is thermally connected at one surface to the heat receiving block, and is engaged with the cover to form a space; a radiation fin part, which is thermally connected to the bottom, has a given shape having at least an air inflow portion, and comprises a plurality of fin parts housed in the space; a centrifugal fan, which has a rotation axis positioned in a neighborhood of the air inflow portion of the radiation fin part, takes in air from the air intake, generates an air flow toward gap portions formed between adjacent fins of the radiation fin part, and generates an air flow along an inner wall of the cover toward the outlet; and heat transfer members, which are arranged such that resistance of the air flow generated by the centrifugal fan toward a side of the radiation fin part becomes smaller, and are inserted through the plurality of fin parts to transfer heat from the bottom.
 2. A heat sink with centrifugal fan of claim 1, wherein: the radiation fin part has a plurality of fin edge portions formed by a plurality of thin plate fins layered at prescribed intervals; the plurality of fin edge portions has the air inflow portion of a semicircular shape opposed to at least the centrifugal fan, a curve portion connecting to the air inflow portion and extending along the inner wall of the cover, and an outlet portion opposed to the outlet.
 3. A heat sink with centrifugal fan of claim 2, wherein: a part of an outer peripheral surface of the centrifugal fan is opposed to the air inflow portion of the semicircular shape of the radiation fin part, and a remaining part of the outer peripheral surface is arranged to oppose the inner wall of the cover, so that the air flow along the inner wall of the cover is generated from a prescribed position of the inner wall of the cover as a start point toward the outlet.
 4. A heat sink with centrifugal fan of claim 3, wherein: the cover has an inflection part of a curve surface forming the inner wall of the cover at a position corresponding to a boundary portion between the air inflow portion and the curve portion of the radiation fin part; and the inflection part causes the air flow along the inner wall of the cover.
 5. A heat sink with centrifugal fan of claim 3, wherein: the radiation fin part has another fin edge portion that is in direct contact with the inner wall of the cover; and an end portion of another fin edge portion in question forms the start point.
 6. A heat sink with centrifugal fan of one of claims 1, wherein: the air outlet is in common with an outlet of the air passing through the radiation fin part and an outlet of the air flowing along the inner wall of the cover.
 7. A heat sink with centrifugal fan of claim 1, wherein: the heat transfer members are arranged in a radial pattern starting from the centrifugal fan.
 8. A heat sink with centrifugal fan of claim 7, wherein: the heat transfer members are arranged such that an air flow blown from the air inflow portion of the radiation fin part, flowing through the radiation fin part, to emerge from the curve portion, does not impede the air flowing along the inner wall toward the air outlet.
 9. A heat sink with centrifugal fan of claim 8, wherein: the heat transfer members are heat pipes.
 10. A heat sink with centrifugal fan of one of claims 1, wherein: the air outlet comprises an outlet for the air passing through the radiation fin part and an outlet for the air flowing along the inner wall of the cover, separately.
 11. A heat sink with centrifugal fan of one of claims 1, wherein: the heat receiving block is provided with at least one heat pipe.
 12. A heat sink with centrifugal fan of one of claims 1, wherein: the air outlet is provided being directed toward an outside of a casing.
 13. A radiation fin assembly, which receives, in a side of the assembly, a swirling air flow sent from a centrifugal fan, and performs cooling by the air flow, wherein: the radiation fin assembly comprises: a plurality of radiation fins layered at intervals; and a group of heat transfer members that are inserted through the layered radiation fins and transfers heat to the radiation fins; the group of the heat transfer members includes a plurality of flat heat transfer members each having a cross section of a flat shape, and the plurality of flat heat transfer members are arranged to be distributed to a plurality of places of the radiation fins; and the flat heat transfer members are distributed such that all or less flat heat transfer members are arranged in such a way that a longitudinal direction of the cross section of the flat shape is inclined with respect to a radius passing the cross section of the flat shape from a center of rotation of the centrifugal fan toward a same rotation direction as a rotation direction of the swirling air flow, to make an acute angle with the radius.
 14. A radiation fin assembly of claim 13, wherein: the flat heat transfer members each have a cross section of an ellipse.
 15. A heat sink with centrifugal fan, wherein: the heat sink with centrifugal fan comprises: a centrifugal fan for sending a swirling air flow from a side of the centrifugal fan; a radiation fin assembly that is positioned on the side of the centrifugal fan and used for cooling by the swirling air flow sent from the centrifugal fan; a heat receiving block that is fixed to the radiation fin assembly, and transfers heat from a heat generating body to be cooled to the radiation fin assembly; and a case member that supports the centrifugal fan, the radiation fin assembly and the heat receiving block, and forms an air flow space; the case member comprises: first and second plate members for forming the air flow space by positioning the radiation fin assembly between the first and second plate members; and a side member that covers a part of a side of a space between the first and second plate members, and cooperates with the first and second plate member to form the air flow space; the radiation fin assembly comprises: a plurality of radiation fins layered at intervals; and a group of heat transfer members that are inserted through the layered radiation fins and transfers heat to the radiation fins; the group of heat transfer members includes a plurality of flat heat transfer members each having a cross section of a flat shape, and the plurality of flat heat transfer members are arranged to be distributed to a plurality of places of the radiation fins; and the flat heat transfer members are distributed such that all or less flat heat transfer members are arranged in such a way that a longitudinal direction of the cross section of the flat shape is inclined with respect to a radius passing the cross section of the flat shape from a center of rotation of the centrifugal fan toward a same rotation direction as a rotation direction of the swirling air flow, to make an acute angle with the radius.
 16. A heat sink with centrifugal fan of claim 15, wherein: the case member has an opening in some side of the case member; and the radiation fin assembly is positioned such that a part of the radiation fin assembly faces to the opening, and another part is opposed to the side of the centrifugal fan.
 17. A heat sink with centrifugal fan of claim 15, wherein: the heat sink with centrifugal fan comprises a plurality of radiation fin assemblies and a plurality of heat receiving blocks fixed respectively to the radiation fin assemblies; the plurality of radiation fin assemblies are positioned on the side of the centrifugal fan.
 18. A heat sink with centrifugal fan of claim 16, wherein: the heat sink with centrifugal fan comprises two radiation fin assemblies and two heat receiving blocks fixed respectively to the radiation fin assemblies; the heat sink with centrifugal fan further comprises a third plate member in addition to the first plate member; a pair of radiation fin assembly and heat receiving block is supported by the first plate member, and the other pair of radiation fin assembly and heat receiving block is supported by the third plate member; and the plurality of radiation fin assemblies are positioned on the side of the centrifugal fan.
 19. A heat sink with centrifugal fan of claim 18, wherein: the third plate member is coupled with the first plate member, being displaceable in a direction of thickness of the third plate member.
 20. A heat sink with centrifugal fan of claim 19, wherein: the case member has a restriction mechanism that restricts a stroke of displacement in the direction of the thickness of the third plate.
 21. A heat sink with centrifugal fan of claim 17, wherein: the case member comprises at least one side having no opening and a plurality of sides having a plurality of openings collectively; the plurality of radiation fin assemblies are arranged such that a part of a peripheral portion of each assembly faces to corresponding opening among the plurality of openings; and another part of the peripheral portion of each assembly is opposed to the side of the centrifugal fan.
 22. A heat sink with centrifugal fan of claim 16, wherein: the case member has a bypass that is formed along a side having no opening, between that side and a side of a radiation fin assembly adjacent to the side in question, to guide a part of the air flow to the opening.
 23. A heat sink with centrifugal fan of claim 16, wherein: the case member has a bypass that is formed along one side having no opening, between that side and a side of a radiation fin assembly adjacent to the side in question, to guide a part of the air flow to the opening; and another side connecting to the one side functions as a guide wall for guiding a part of the swirling air flow from the centrifugal fan to the bypass.
 24. A heat sink with centrifugal fan of claim 15, wherein: the heat receiving block comprises a heat receiving portion that is thermally connected to a heat generating body to be cooled and a heat transfer portion for transferring heat of the heat receiving portion to the radiation fin assembly.
 25. A heat sink with centrifugal fan of claim 15, wherein: the flat heat transfer members each have a cross section of an ellipse. 